Metroids are one of the major elements and creatures in the Metroid series of games. They are some of the more feared species in the series, as they often appear in dark stages and attach themselves onto your face to suck out your energy.

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History

The species were created by the Chozo, and named them Metroid apparently because the name means "ultimate warrior" in their language.

They created them so that they could be protected from the X Parasite by sucking out their victim's life energy. This allows them to kill the parasites without dying themselves.

A graph of a Metroid life cylcle. Click to enlarge.

However, their project went awry when the Metroids started to become more vicious and started to attack the Chozo forcing them to leave the planet. Even though it was supposed that the Chozo were killed by the Metroid, the remake of Metroid II: Return of Samus, Metroid: Samus Returns reveal that the Chozo who created the Metroid were betrayed by some of their own and were killed by an unknow masked Chozo warrior armed with a Power Beam canon.

Once a Metroid is born, it considers the first being it sees to be its mother, much like most real life animals do. This can be seen in Metroid II: Return of Samus and Super Metroid, where a newly hatched baby Metroid looks to Samus Aran, the protagonist of the series, as its mother, as normally a newborn would attack her or any other living being. It can thus be concluded that they have a form of intelligence seeing that they have a thought process.

In time, a Metroid will start to morph (the life cycle of a Metroid can be seen to the left) into larger and more powerful creatures. All of the species to the left have been seen as enemies in the Metroid series.

Metroid/Zero Mission

In Metroid and Metroid: Zero Mission, it is revealed that the Metroid were discovered by the Galactic Federation who managed to capture some Larvae from SR388's surface despite suffering some heavy casualities. The Metroid specimens were soon stolen by the Space Pirates who discovered that the creature would multiply when exposed to beta radiations. With the Metroid by their side, the Space Pirate gained the upper hand in their fight against the Galactic Federation who was unable to get rid of the creatures. Samus Aran was then tasked with singlehandedly infiltrating the Space Pirate base Tourian on Zebes and destroy the Metroid found there as well as Mother Brain, a Chozo A.I. who allied herself with the Space Pirates and became their commander.

Metroid Prime

Not all Metroid larvae were destroyed during the events of Metroid and some were transported to Tallon IV by the fleeing Frigate Orpheon. The Metroid Larvae being very sensible totheir environment began to mutate into a new breed refered to as "Tallon Metroid", which appears to be smaller and seemingly never grow into the next phase of their life. These Metroid have a very unstable genome however and can mutate greatly if exposed to Phazon and have a very high chance of surviving said exposure with new, useful mutations. After discovering this, the Metroid became one of the favorite test subject of the Space Pirate who were responsible for the creation of many new species of Metroids during the events of Metroid Prime. Two of the main ones found on Tallon IV being the Hunter Metroid and the Fission Metroid. A higly mutated Metroid known as Metroid Prime also serves as the main antagonist of the game. According to in game lore, Metroid Prime was already a threat when the Chozos were still on Tallon IV and is one of the reason the Impact Crater was sealed. Samus eventually defeat Metroid Prime who manage to steal her Phazon Suit and DNA to be reborn as some sort of Human-Metroid hybrid known as Dark Samus.

Metroid Prime 2: Echoes

In Metroid Prime 2: Echoes, the Space Pirates imported Metroids Larvae from Tallon IV to planet Aether. The planet's environment and stimuli seemingly caused the creatures' membranes to gain a red coloration while retaining all of the particularities of the Tallon IV breed. The Metroid were brought to Aether by the Space Pirates in hope of continuing their genetic experiments on them.

Many of these Metroid Larvae were inevitably possessed by the Ing and became Dark Tallon Metroid through symbiosys, a breed able to survive to the rash environment of Dark Aether. The Space Pirate base in Agon Wastes contains a room filled with artificially-created Tallon Metroid Cocoons, which give them an infinite supplies of Tallon Metroid to experiment on, it is also worth mentioning that these Tallon Metroids quickly become Aetherian Metroids whenn they are exposed to Phazon. Dark Samus also serves as one of the main antagonists of the game as well as the final boss.

Metroid Prime 3: Corruption

Since Metroid Prime 3: Corruption revolve mainly around Dark Samus and her plan to corrupt the universe with her Phazon infused Leviathan Seeds. Aside from Dark Samus, four additional mutant strains of Metroid are introduced. All are once again variants of the Tallon Metroids as they are very sensible to Phazon.

This time, the Space Pirates are under the direct influence of Dark Samus who took over the Pirate Homeworld and started to request progressing futher on their genetic experiments. The four breeds are the Phazon Metroid, the Miniroid, the Hopping Metroid and the Metroid Hatcher. Dark Samus herself is seemingly killed at the end of the game and every single Phazon infused creatures seems to die as well, killing all of the mutated Tallon Metroid breeds.

Metroid Prime: Federation Force

The Space Pirates maintained a supply of Metroid eggs and Larvae, multiplying the latter in a former medical laboratory on Talvania. All of the Metroids present, including the Pirates themselves, were enlarged with the Amplification beam. The Galactic Federation caught wind of this operation and tasked the Federation Force with destroying the facility via a self-destruct mechanism inside. The force was also tasked with retrieving Metroid eggs by General Alex Miles. At the end of the game, an unknown individual with an armor similar to the one usually worn by Sylux infiltrates a Galactic Federation laboratory, and causes a Metroid Egg in captivity to hatch.

Metroid II: Return of Samus/Metroid Samus Returns

In Metroid II: Return of Samus and Metroid: Samus Returns, seeing the dangers the Metroids posed to the galaxy in the past, the Galactic Federation sent the Special Squadron to SR388 to wipe out the hostile lifeforms. After two failed attempts by the Federation's army to eradicate the Metroids on their home planet, they called on Samus Aran to deal with them as she was the only person able to survive several encounters with the creatures.

Since the SR388 Metroids are the original ones, they go through their natural growth cycle and eventually becomes the feared Omega Metroid who are pretty much the apex predator of SR388. Samus manage to kill every single Metroid on the planet and their queen and decide to bring the last infant Metroid with her to have it in captivity. She is stopped by Ridley, who is starting to regenerate out of his cyborg form he had in the Prime games due to his defeat iin the original Metroid, but with the help of The Baby, she is able to defeat him and he is left for dead on SR388. Ridley finish his regeneration and leaves his cybernetic parts on the planet before leaving for the Ceres Station where Samus left The Baby. Since the Metroids are gone, the X Parasite start to take over SR388 and reclaim their place as the original apex predator of the planet.

Super Metroid

In Super Metroid, The Baby is at Ceres Station where it is studied by human scientist but mere minutes after Samus leaves the station, Ridley arrives with the Space Pirates forces and take steal The Baby to take it to their rebuilt base on Zebes. The Space Pirates uses their usual beta radiation method to multiply The Baby. They also try to clone the multiplied Metroid Larvae, which result in the failure known as Mochtroid. Samus eventually ffinds out that The Baby was mutated into a giant Metroid, The Baby sacrifice itself to help Samus take down Mother Brain.

Metroid Other M

After Samus Aran completed her second mission on Zebes, she spends a great deal of time in thought, reliving the death of the Baby at the hands of Mother Brain. Adrift in space and in memories, she receives a message codenamed "Baby's Cry", reminding her of her lost "child". Following the signal, Samus arrives at the BOTTLE SHIP.

In the Cryosphere, Samus finds a deceased Gigafraug showing signs of Metroid predation. Samus has doubts since not only would Metroids perish in the Cryosphere's cold temperatures, they were extinct thanks to the efforts of both the Space Pirates and herself.

Soon afterward, MB, posing as Madeline Bergman, tells Samus about "Project Metroid Warriors", in which Metroids were cloned from the Baby's particles that landed on Samus's Power Suit and are located in Sector Zero. She also explains that they made an AI of Mother Brain's intelligence to control them.

Samus heads to Sector Zero but stops short as an Infant Metroid pops up in front of her, reminding her of the Baby. When Samus decides to kill the Metroid, Adam Malkovich shoots her in the back; the Infant sees her as food, but is also shot.

Adam explains that the cloned Metroids that have reached the mature larval stage are likely to have been re-engineered to remove their vulnerability to cold, making them virtually unstoppable; this also confirms that the dead Gigafraug Samus found earlier was indeed the subject of Metroid predation. He also states that the breeding project was named after him, though he was not actually involved in the project. He was petitioned for the authority to create the project, but he refused. However, scientists co-signed it to get the project running.

Adam shot Samus earlier to prevent her from interfering with his next course of action: because the Metroids are immune to Samus' weaponry, Adam goes to activate a self-destruct protocol on Sector Zero by causing severe damage from within, which detaches the sector from the station before the explosion. Seeing this as a suicide mission, Samus attempts to convince him to let her destroy the Metroids, but Adam ignores her, saying that she has work left on the BOTTLE SHIP. Adam succeeds in his mission to destroy the Metroids at the cost of his own life.

However, a Queen Metroid was kept in another part of the BOTTLE SHIP. It not only attacks Samus, but launches several other Metroids. Ultimately, Samus is forced to resort to an old tactic and uses a Power Bomb in the belly of the beast. it is currently unknown how MB succeeded in making an Infant Metroid reach the Queen stage outside of SR388's environment.

Metroid Fusion

While the Metroid were gone from SR388, the ecosystem went out of balance and the X parasite regained their place as the apex predator. Samus was hired to protect some Federation scientists who were studying the recovery of the SR388 ecosystem. While they were on the planet, Samus was infected with an X Parasite. She was rushed back to Federation Headquarters with a minimal chance of survival. It had recently been discovered that the Metroids were the sole predators of the X Parasites, without the former to keep them in check, the X are rapidly reproducing and infecting all forms of life on the planet, taking their hosts' DNA in order to mimic them before moving on to their next host. Using this information, the Federation saved Samus by injecting her with a Metroid vaccine made from a DNA sample of The Baby.

Now with Metroid DNA, Samus is immuned against the X Parasite and is able to absorb them in their pure form just by making contact with them. This caused her to inherit the Metroids' weakness to cold however. Samus quickly realised that if the X Parasite managed to gain access to a single host with the ability to pilot a ship, they would be able to decimate the galaxy.

During her mission, she discovered that the Galactic Federation tried to breed Metroids once again but before she could do anything about it, the program was destroyed by a powerful X Parasite mimicking Samus known as the SA-X. The whole laboratory was ejected into space killing all of the Metroids except for one infant that managed to escape and grow to the Omega stage of its life before being killed by Samus. After that, the only remaining sample of Metroid DNA known is inside Samus herself.

Types of Metroids

Natural Types of Metroid

The first form of a regular Metroid. They are what the word "Metroid" is usually used to refer to. They are floating jellyfish-like cratures with three fangs and the ability to grasp onto its opponents.

The second form of a regular Metroid. The top, bluish glowing part of a regular Metroid seemed to have gone down to his underside. Also spawned legs, which allow it to walk around. Once a Metroid turns into an Alpha Metroid, it looses its ability to grasp onto its opponents.

The fourth form of a regular Metroid and the form that a Gamma Metroid will turn into. It's about the size of a human, though a little taller. Arguably it could be considered the biggest change in all the forms that a Metroid goes through.

The fifth form of a regular Metroid, and the form that a Zeta Metroid turns into. Much larger than a human, and in appearance looks like a dinosaur. When a Zeta Metroid turns into this form, it is not only more powerful, but it also gains the ability to shoot fire balls from its mouth.

Hunter Metroids are Tallon Metroids that grew up in a Phazon heavy environment, instead of becoming Alpha Metroids, they turned into these floating Metroids with the ability to drain life force from a confortable distance.

These Metroids are actually one of the few breeds that developed a complete life cycle after being exposed to Phazon and thus becoming a new species. The Miniroid are harmless and relly on the protection of their elder, the Phazon Metroid to survive. They are the equivalent of the Metroid Larvae.

These Metroids are the second phase in a Miniroid's life, they are agressive and act as protector to the smaller Miniroids. They are the equivalent of all the stages in a regular Metroid's life beyond the initial one.

Failed clones of the regular Metroids that are weaker in every way, it is unknown if they are even able to advance further on their intended life cycle.

Unique Specimens

Queen Metroid

In all, only two Queen Metroids has been found (in the Game Boy video game Metroid II: The Return of Samus and in Metroid: Other M). It seems to be the largest of the Metroid species found in the life cycle above, and currently it is unknown what makes a Metroid turn into a Queen Metroid. The Queen Metroid found in Metroid II is a very strong creature that is capable of tearing its opponents apart easily using its long, expandable neck to grasp onto far away prey.

Metroid Prime/Dark Samus

Artwork for Metroid Prime.

Metroid Prime is the main antagonist and final boss of Metroid Prime. Apparently, according to the official website at least (which could arguably be considered cannon), Metroid Prime also came from SR388. It was also revealed via the Chozo lore that can be found in the series that Metroid Prime is one of the major reasons why their species started to become extinct.

It should be noted that if we are to believe this, Prime arrived on Tallon IV long before the events that took place in Metroid Prime, which would mean that at least one Metroid was on Tallon IV before the arrival of the Space Pirates. After being defeated at the hands of Samus Aran, the creature was able to regenerate itself and turn into the being known as Dark Samus, who would permanently die in Metroid Prime 3: Corruption. Metroid Prime is the most advanced, intelligent and dangerous Metroid featured in the entire series so far and one of the few Metroid character that is considered the main antagonist of three separate games.

Super Smash Bros. series

In Super Smash Bros. Brawl, the Metroid Larva is an Assist Trophy. The form it most resembles is the Zeta Metroid. When summoned, it floats around and targets a nearby opponent and attacks to them with very light damage and stuns them repeatedly restricting their movement. Eventually, the Metroid comes off and sometimes attacks another opponent. If not, it will just disappear. In the trophy, the reflection of Super Metroid can be seen on it. In Super Smash Bros. for Nintendo 3DS and Wii U and Super Smash Bros. Ultimate, it returns as an assist trophy. Dark Samus, who is technically a type of Metroid is also a playable character in Ultimate.

Trophy Descriptions

Super Smash Bros. Melee

A parasitic life form that can absorb all types of energy, Metroids have strong resistance to most conventional weaponry. To defeat them, Samus Aran had to freeze them with Ice Beam shots and then blast them with missiles. Mochtroids, which look like Metroids, are weaker, with fewer internal nuclei.

Super Smash Bros. Brawl

A bioengineered life-form found on planet SR388. Metroids attach to organisms and drain life energy. The Galactic Federation commissions Samus to eliminate them, but Space Pirates try to harness their power. One of the few ways Samus can kill Metroids is by shooting them with the Ice Beam and then shattering them with missiles. The Metroid's cry is chilling and indescribable.

Super Smash Bros. for Nintendo 3DS and Wii U

EU:Mysterious floating life-forms, discovered on the planet SR388, that absorb energy from other living beings. They're tough, except when they're cold. In this game, they'll try to attach themselves to fighters' heads and drain their energy. Press all the buttons you can to shake them off!

NA: First discovered on planet SR388, this floating life-form grows by absorbing energy around it. It is incredibly durable but extremely weak to cold. In Smash Bros., a Metroid will grab a rival by the head and drain energy. If you get grabbed, shake it off by pressing left and right!